1) Technical Field of the Invention
The present invention relates to a power semiconductor device, and in particular, relates to the power semiconductor device for controlling a motor used for, e.g., an electrical car.
2) Description of Related Arts
Recently, so called a hybrid-power car utilizing both of an engine and a motor has been commercialized, which requires an engine system dedicated for an automobile and an hybrid system including components such as a motor, an inverter device, and a battery, to be packed in a limited space such as an engine and trunk room. Therefore, demand for downsizing those components is intensive, and minimizing the semiconductor device in size is eagerly desired as well.
While the power module incorporated in the power semiconductor device has to be mounted on a radiating fin for radiating heat generated from the power module, in general, a plurality of the power modules are mounted on a wide surface of the radiating fin in a two-dimensional manner. However, this planner arrangement of the power modules limits flexibility in designing the total layout of the power modules, thereby inhibiting to downsize the power semiconductor device.
Also, when the power module having a mold package and a radiating surface is mounted on the radiating fin with the radiating surface closely contacted thereon, the mold package is directly screwed with the radiating fin. The long-term fastening force may cause the mold package to be crept in the local region where the force is applied, thereby loosening the screws. In order to avoid creeping the mold package, a metal plate having high rigidity is typically provided between the power module and the radiating fin which are together to be screwed, for distributing the fastening force by the screws equally across the mold package. However, this approach is not sufficient to prevent the screws from being loosened due to the resin creeping.
Several power semiconductor devices have been proposed, and for example, JPA 06-024279 discloses a cooling device for an electric automobile, in which a plurality of power modules is mounted on a radiating plate. Another reference, JPA 2003-333702 discloses a motor controller having a plurality of semiconductor elements provided on the heat sink. In JPA 2004-215340, the power installation structure for an inverter device is disclosed having the power modules provided on the U-shaped radiating plate. Also, JPA 2002-216860 discloses a cylindrical cooling jacket. Further, JPA 2003-338592 discloses a power semiconductor module having a coil spring provided between the power module and the control board.
Thus, the present invention was made for addressing those problems as described above, and one of the aspects thereof is to provide a downsized power semiconductor device having a plurality of power modules mounted on a radiating fin.